This invention relates to electrical switching devices and more particularly to electrical switching devices with arc chute covers which are resiliently and yieldingly clamped by a clamping device.
In known arrangements of the above type (DE-GM 75 22 823, DE-AS 1 077 296) arc chute covers are pressed onto bases by means of springs. In the first case, a helical spring is guided in each case over a quick release fastener. In the second case, a leaf spring is used for pressing cover and base together. The springs provided in both cases can certainly compensate for tolerances in the manufacturing of the arc chute covers, so as to avoid damage to the chute covers during securement, but they cannot be used, at least not satisfactorily, for allowing the chute cover to breath, i.e. for allowing the arc chute covers to lift for a short time from the base part when high excess pressures occur due to arcing. If the spring were to be of weak construction, then when there is a great excess pressure the spring would be compressed flat almost immediately, unable to absorb further pressure and the resulting impact exerted on the arc chute cover could cause damage to the cover. If, on the other hand, the spring is made too rigid, then the actuation force for locking the arcing chamber is too great and no relief can be expected when there are only low excess pressures.
It is an object of this invention to provide an arc chute cover for a switching device which is secured in such a manner as to reduce excess pressures from arc heated switching gases. It is a furthr object of this invention to provide relief from excess pressures of arc heated gases without damaging the arc chute cover or the clamping device holding the cover to the base.